Hydraulic device for interlocking two hydraulic piston-cylinder units



J. L. GRATZMULLER HYDRAULIC DE Aprll 24, 1962 3,030,930

VICE FOR INTERLOCKING TWO HYDRAULIC PISTON-CYLINDER UNITS Filed March 20, 1957 9 5 5 7 2 1 .Il m 1 F 7 f 5 1. 2 8 3 H l I! O N l3 5 B 2 2 1+ 9 1 1 a L 7H H T $52 4 6 J 2 2 3 1 1 1 1 9 1 7 w 1 United States Patent 3,030,930 HYDRAULIC DEVICE FQR INTERLOCKING TWO HYDRAULIC PISTON-CYLINDER UNITS Jean Louis Gratzmuller, 30 Ave. Georges Mandel, Paris, France Filed Mar. 20, 1957, Star. No. 647,348 Claims priority, application France Mar. 27, 1956 4 (Claims. (Cl. 121-40) This invention relates to a hydraulic device for interlocking two hydraulic piston-cylinder units, or an equivalent system, associated with a same movable structure for actuation of the same in two opposed directions.

One object of the invention is to ensure a hydraulic locking of both units and, hence, of the movable structure, at any time except when this assembly is being operated.

Another object of the invention is to design the hydraulic locking device in such a manner that feeding of pressure fluid in one of the units is both necessary and sufiicient to automatically ensure unlocking of the whole system.

Both of these objects aim at avoiding any unwanted displacement of the movable structure, in particular from its end-of-stroke positions, which is essential in certain applications, such as the control of disconnecting switches.

It is another object of the invention to provide a hydraulic locking device capable of fulfilling the two abovedefined conditions, while being of extremely simple construction.

The hydraulic locking device according to the invention is essentially constituted, for each unit, by a nonreturn valve controlling its feeding duct, a normally-closed exhaust valve and a control means responsive to the pressure in the feeding duct of the other unit and operatively associated with said exhaust valve to open the same as said other unit feeding duct is fed with pressure fluid.

With this arrangement, when none of the units are operated, the hydraulic fluid contained in each one of said units is imprisoned therein and the whole system is locked. However, as soon as one of the units is fed with pressure fluid for actuating the movable structure, the exhaust valve of the other unit is automatically opened, which is both necessary and suflicient to permit the actuation.

It is a more particular object of the invention to design the control means associated with the exhaust valve of each unit, as a sliding valve subjected on one of its faces to the pressure in the feeding duct of the other unit and, on its other face, to the pressure in the exhaust duct of the unit associated with said exhaust valve, the sliding valve being adapted to successively open the exhaust valve and then, establish the feeding circuit of the other unit.

It is a further object of the invention to locate the admission and exhaust valves in housings directly provided in the wall of the units, so as to reduce to a minimum leakages from the active compartments of the units.

In the above-defined hydraulic system, the locking of each unit is ensured by a mass of liquid imprisoned in a space, tightly closed by two valves. Now, when the locking is meant to subsist during long periods, such as in the already mentioned application to the control of disconnecting switches, the mass of liquid may be subjected to important temperature increases capable of re sulting in the building-up of an objectionable pressure due to thermal expansion of the liquid. As a specifiic example, in an existing disconnecting switch-hydraulic control, with the working pressure being about 450 kg./ cm. it has been observed that, in certain periods of the year, and in particular during the warm hours of the day, the pressure of the liquid imprisoned in the system could reach 1,200 kg./cm. thus subjecting the units to the risk of possible destruction.

Another object of the invention is therefore to supply each one of the above-defined closed spaces with a safety valve calibrated at a pressure sufficiently high to ensure the hydraulic control and locking with safety, yet low enough to avoid any deterioration of the system.

Now, in certain applications, such as the already mentioned control of disconnecting switches, it is interesting to dispose of a hand-control system.

Then the operator must be informed when an order has been completed. In other Words, when the operator has actuated his hand-control, the hydraulic transmission should supply a sufficient amount of pressure liquid to ensure a displacement of the movable structure by the units along the whole intended stroke. It will easily be understood that these conditions Will be surely met if, in response to the actuation of the hand-control, the hydraulic source supplies an over-reaching amount of pressure liquid.

It is, therefore, a further object of the invention to associate with the active compartments of the piston cylinder units, an intercommunication duct, both ends of which duct are controlled by non-return valves preventing liquid from flowing from the duct towards the relevant units, while the pistons of the units are associated with a pushing member capable of unseating the corresponding non return valve when the movable structure has been brought into one of its end-of-stroke positions.

Since the return stroke of each unit is ensured, through the kinematic linkage interconnecting the unit pistons, under the control of the other unit when the latter is fed with pressure liquid, which implies that the first-mentioned unit has its exhaust valve opened, the controlled opening of the associated non-return valve by the pushing member of the said first unit sets the active compartment of the said other unit into communication with the exhaust system, whereupon an excess of liquid may be sent, if desired, into the said active compartment. Moreover, when liquid is no longer fed into said compartment, the whole assembly remains blocked until a new feeding of liquid again causes unlocking.

It is thus clear that, on the one hand, the presence of the above-described intercommunication duct does not suppress the unlocking effect while, on the other hand, it permits sending into one of the units a super-abundant amount of liquid, the excess of which will be discharged towards the liquid tank as soon as the movable assembly reaches the end of its stroke.

Another essential advantage of the above-described system is that the hydraulic locking of both units is ensured not only at both of their end-of-stroke positions, but also in any intermediate position, in case of any failure in the system. This facility offered by the present device meets in particular one of the conditions to be fulfilled in a control adapted to be used for disconnecting switches, which control requires, in the case of unexpected jamming of the movable contact structure of such a switch in an intermediate position that the said structure cannot undergo any unwanted displacement.

Other objects and advantages of the invention will be hereinafter described with reference to the accompanying drawings, given merely by way of example.

In these drawings:

FIGURE 1 is a diagrammatic view of a device according to the invention;

FIGURE 2 shows a modification adapted to manual control.

In both figures, the corresponding elements have been designated by the same references.

1 and 2 are the cylinders of two single-acting units, the respective pistons 3 and 4 of which are operatively 3 connected with a same movable structure, diagrammatically shown at 31, in such a manner that the active stroke of the piston 3 brings the said structure from one endposition to the other, while the active stroke of the piston 4 brings the said structure back from the said other endposition to the first position.

The cylinder 1 is fed with pressure liquid through a duct 5 under the control of a non-return valve, such as a ball 6. Exhaust of liquid from cylinder 1 is ensured by a duct 11 communicating with a tank (not shown) under the control of an exhaust valve 12.

Similarly, the cylinder 2 of the other unit is fed through a duct 13 controlled by a non-return valve 14 while exhaust of liquid therefrom is ensured by a duct 15, communica-ting with the tank under the control of an exhaust valve 16.

The duct 5 is controlled by a sliding valve 7, sliding member 8 of which is subjected to the action of the pressure in a feeding duct 9. The sliding member 8 carries, moreover, a pushing-rod capable of unseating the ball 16 before the sliding member 8 has sufiiciently moved towards the left (in the drawing) for uncovering end 5' of the duct 5.

Similarly, the duct 13 feeding the second cylinder 2 is controlled by a sliding valve 17, sliding member 18 of which carries a pushing-rod 19 capable of unseating the ball 12 and then uncovering end 13' of the duct 13. To urge the sliding members 8 and 18, as well as the valves 6, .12, .14 and 16 towards their seated position, any conventional means, such as the springs shown in the drawings, may be used.

Furthermore, in the example shown, the two active compartments of the cylinders 1 and 2 are provided with safety discharge valves 20 and 21 respectively, loaded by springs 22 and 23 respectively, so as to open at a pressure higher than the maximum workin pressure contemplated but still sufiiciently limited to eliminate any risk of deterioration of the system due to overpressure.

This device operates as follows: when no pressure prevails in the system, the four valves 6, 12, 14 and 16 are seated, so that a mass of liquid is imprisioned in the cylinders 1 and 2 thereby locking the Whole assembly.

When, under such conditions, the movable structure is to be displaced, e.g., in the direction of the arrows of FIG. 1, it sufiices to send liquid into the feeding duct 9; this liquid first causes shifting of the sliding member 8, which successively opens the valve 16 and establishes a communication between the ducts 9 and 5. Through this last duct, the liquid is finally sent into the cylinder 1 under opening of the valve 6. The piston 3 of the cylinder 1 is displaced in the direction of the arrow which, through the kinematic linkage 31, also causes a displacement of the piston 4 in the opposite direction (as also indicated by an arrow). This last displacement is made possible by the above-described opening of the exhaust valve 16 permitting discharge towards the tank through the duct 15 of the liquid previously contained in the cylinder 2. When the stroke of both units is completed, the liquid which has ensured this displacement is imprisoned'in the cylinder 1 due to the reclosing of the valve 6, and so on.

In FIG. 2, 24 and 25 are non-return valves normally held on their seats by springs 26 and 27' respectively and each being mounted at one end of a common duct 28, interconnecting the active compartments of the cylinders 1 and 2. On the other hand, the pistons 3 and 4 of the said cylinders are provided with abutment studs 29 and 30 adapted to unseat the valves 24 and 25 respectively, through pushing-rods 32 and 33 respectively, as the said pistons respectively reach the end of their strokes.

The kinematic linkage 31 is so designed that when one of the pistons 3 and 4 reaches the end of its active stroke, the said linkage has brought the other pistonback to the origin of its own active stroke.

Under these conditions and in particular in the embodiment of FIG. 2 if, for example, the unit 1 is fed from a suitable pump under the control of a hand actuator with an amount of liquid greater than that required to bring said unit to the end of its stroke, the piston 4 of the other cylinder 2 will be safely brought a fortiori to the origin of its own stroke, position in which it will ensure opening of the non-return valve 25. Furthermore, the cylinder 1 W111 be further fed with liquid, since the amount of liquid sent into the said cylinder by the pump is superabundant. As a result, the sliding member 8 of the sliding valve 7, then in a position for which it establishes the feeding circult of the cylinder 1, will hold open the valve 16 through its pushing-rod 10 and, hence, the active compartment of the cylinder 2 in communication with the exhaust system. Therefore, the excess liquid flowing into the said compartment through the intercornmunication duct 28, as indicated by the arrow in dash lines, is discharged towards the tank through the exhaust duct 15 of the cylinder 2 and through the open valve 16.

It is clear that the operation of the device is symmetrical and that, if the cylinder 2 is fed in turn with liquid, in order to bring the movable structure into its other end-of-stroke position, as the piston 3 reaches the origin of its active stroke, it places the duct 28 and, hence, the active compartment of the cylinder 1, into communication with the exhaust system.

Thus, any operation of the manual actuator determines a complete stroke in either direction of the movable structure 31. Furthermore, this arrangement does not destroy the hydraulic locking of both units, not only in their end-of-stroke positions, but also in any intermediate position in the case of a failure in the system since, for any position of the whole assembly, except for the end-ofstroke positions, the non-return valves 24 and 25 are held closed by their respective springs 26 and 27 so that, if the system tends to be displaced from any one of its end-of-stroke positions, the resulting immediate closing of that non-return valve which is then open, immediately causes hydraulic locking of the system by the mass of liquid imprisoned in the active compartment of the relevant unit.

In a general manner, While in the above description is disclosed what is deemed to be practical and efficient embodiments of the invention, it is to be understood that the invention is not limited thereto as changes may be made in the arrangement, disposition and form of the parts without departing from the principle of the present invention.

In particular, it is obvious that the hydraulic interlocking device according to the invention may be used, not only in association with two single-acting hydraulic units, as described above, but also with one single doubleacting unit, differential or not; as a matter of fact, such a double-acting unit is the equivalent of two single-acting units having one common cylinder, and the pistons of which would be integral with one another. The same locking device may be also associated with two sets of any number of single or double-acting units, provided that the same are operatively connected with one same movable structure for actuation thereof in two opposed directions.

In the appended claims the expression hydraulic unit will be used to designate either one or more single-acting units actuating a structure in a same direction or, again, each of the opposed structures of a double-acting unit.

What is claimed is:

l. A hydraulic device for automatically locking in any point of their stroke two piston-cylinder units operatively connected with a same movable structure for actuating of the same in opposed directions, said device comprising, in combination, for each one of said units, a feeding duct, a non-return valve incorporated in said feeding duct, a normally closed exhaust valve, control means responsive to the pressure in the feeding duct of one of the units to open said exhaust valve of the other unit when said pressure reaches a predetermined value and said control means being defined by a sliding valve having a sliding member adapted to successively open the exhaust valve of the associated piston-cylinder unit and establish the feeding circuit of the other piston-cylinder unit.

2. A hydraulic locking device according to claim -1, further comprising a discharge valve associated with each one of said piston-cylinder units, said valve being loaded to open at a liquid pressure in the corresponding pistoncylinder unit materially higher than the maximum working pressure, to avoid any risk of deterioration due to overpressure.

3. A hydraulic locking device according to claim 1, further comprising a duct interconnecting said piston cylinder units, a first additional non-return valve incorporated in said duct to prevent liquid from flowing from said second unit into said first unit through said duct, a second non-return valve incorporated in said duct to prevent liquid from flowing from said first unit into said second unit, pushing means interposed between the piston of said first unit and said first non-return valve to open the same as said piston of the second piston-cylinder unit reaches the end of its active stroke and pushing means charge line connected to each cylinder of said pistoncylinder units to allow pressure liquid to flow therefrom, a non-return valve for each of said supply lines, a normally closed exhaust valve for each of said discharge lines, said non-return valves and exhaust valves being adapted to prevent flow of pressure liquid from said cylinders through said supply and discharge lines, control means responsive to liquid pressure in the supply line connected to one of said cylinders including means for opening the exhaust valve in the discharge line connected to the other cylinder prior to liquid pressure in such supply line opening the non-return valve for the supply line for said one cylinder, and second control means responsive to liquid pressure in the supply line connected to the other cylinder and including means for opening the exhaust valve in the discharge line connected to said one cylinder prior to liquid pressure in such supply line opening the non-return valve for the supply line for said other cylinder.

References Cited in the file of this patent UNITED STATES PATENTS 1,550,550 McCauley Aug. 18, 1925 1,969,736 Erling Aug. 14, 1934 2,362,339 Armington Nov. 7, 1944 2,389,654 Van Der Werfr Nov. 27, 1945 2,401,258 Livers May 28, 1946 2,410,978 Kelly Nov. 12, 1946 2,625,168 Charlson Jan. 13, 1953 2,648,346 Deardorir et a1 Aug. 11, 1953 2,717,652 Nichols Sept. 13, 1955 

